The present invention relates to a solid or water quantity measurement apparatus using microwaves for the measurement of the solid quantity and/or water quantity of liquid or viscous material such as cow's milk and soy which include solid material and water.
Cow's milk comprises some quantity of fat, protein, milk sugar, ash and water, the quantity of which is not always constant. The content changes according to breed of cows, feed, season, condition of cows health and others. Thus, it is best in business to decide the price of cow's milk in accordance with the contents of the milk. However, measurement of the content requires a relatively long time. Therefore, the determination of the milk price depends on the measurement of fat at the present time. The fat measurement requires relatively short time. (Official methods for measurement, such as the Gerber method and the Babcock method, require about 2 hours / 12 samples, and its photo-turbiditymeter method, which uses a milk checker or a milk tester, requires about 20 seconds / 1 sample.)
There was in the past a relationship between the quantity of the fat of cow's milk and the quantity of other materials in the milk, and the latter was proportional to the former. However, there is no relationship between the fat quantity and other materials in cow's milk today because cows which produced milk of small quantity of fat have been reduced and those producing milk of large quantity of fat have been increased. As a result, cows which produce milk of large quantity of fat are today being normally fed at farms. Those cows sometime produce milk of small quantity of solid materials (milk sugar, protein and ash) in spite of large quantity of fat, and this is a serious problem.
Recently, therefore, it has been suggested that the transaction of cow's milk should be determined on the basis of measurement of total solid quantity, including fat and other all solid materials, although the transaction on the basis of respective quantity of each material in the milk is best. However, the official measurement method of total solid quantity of the milk is its heat drying method which requires 7 hours to 8 hours for the measurement. Thus more than ten or more samples can not be measured by the heat drying method in a day.
There are other methods for measurement, for example, specific gravity meters, lactometer methods, plastic bijou methods, Mojonnier methods, infrared rays total solid measurement methods, microwave heating methods and microwave heating water meter methods.
The specific gravity meter method includes the measurement of specific gravity of cow's milk and estimation of total solid quantity rate of the milk. However this method is not accurate enough to utilige in the transaction of cow's milk. The total solid rate in the milk can be shown and temperature compensation introduced into the measured value of the total solid rate by the lactometer method. However this method gives errors as much as .+-. 0.12 % TMS (TMS: Total milk Solid.). The plastic bijou method utilizes 10 bijous of 10 colors made of poly-methyl-styrene, each of the bijous corresponding to a the specific gravity difference of 0.001. Specific gravity of cow's milk can be determined by numbers and colors of bijous above, and under the surface of the milk. Thus, the plastic bijou method is practiced easily but is inaccurate. The Mojonnier tester method includes the preliminary heating of cow's milk at 180.degree. C on a plate, main heating at 100.degree. C .+-. 1.degree. C in a vacuum furnace after preliminaryheating, and cooling after the main heating and measurement of a solid remaining on the plate. This method can be carried out speedily however, it is costly and gives measurement deviation from that of the official method. Thus the Mojonnier tester method has been rarely practised. The infrared rays total solid measurement method includes impregnation of cow's milk of 0.97 ml which corresponds to 1g weight into a filter paper, preliminary heating of the filter paper on a alminum plate and heating (75.degree. C) in an infrared ray furnace to evaporate water. The infrared ray furnace is not sealed hermetically, so that the dryed sample in the furnace absorbes water in the air. The time interval between drying the sample and measurement of the quantity of the dryed sample is not constant because of the manual transportation of the sample from the drying stage to the measurement stage. This causes a difference in the absorbed water among the dryed samples at the measurement stage and the absorbed water effects its measurement accuracy. The calculation of %TMS requires 3 members in this method with manual calculation. More than 300 samples can not be measured in a day.
The microwave heating method employs a so-called electron range (microwave oven) to dry the cow's milk. The microwave oscillator is separated from the microwave oven because of the higher power of the drying sample of milk. Since the microwave drying method merely utilizes microwave heating instead of the air flow heating of the official method, it requires the same steps for the solid measurement of the official method. As a result, it requires a relatively long time for measurement. Also, a turn table is required in the oven because the electric field destribution in the range is not uniform. This makes it impossible to achieve a balance in the oven. Thus, direct reading of the balance in the oven is impossible. In addition, its temperature in the oven rises in accordance with the repeating of the measurements. Moreover, the wall surface of the oven is relatively low in temperature, which causes condensation of evaporated water. Thus, condensed water falls on the sample. The microwave drying method is thus a complex process.
The microwave heating water meter method employs the same theory as the microwave heating method as described above. However, a balance is achieved with the microwave oven, and thus the sample is not required to be carryed out of the oven to measure its weight, and direct reading of the weight of the sample is possible by the balance. Nevertheless, the temperature in the oven rises as its measurements are repeated. This has an effect on the accuracy of the measurement. Also, electric field distribution in the oven is insecure and not uniform. Therefore a stirrer is required. A large quantity of the sample milk is required, and condensed water appears on the surface of the oven.